(1) Field of the Invention
This invention relates to a heat treatment apparatus for polyolefin resin particles. Specifically, the present invention relates to an apparatus for heating and agitating polyolefin resin particles in the presence of an aqueous medium and dispersing agent in an autoclave so as to subject the resin particles to a heat treatment or an apparatus for heating and agitating polyolefin resin particles in the presence of an aqueous medium, dispersing agent and crosslinking agent in an autoclave to subject the resin particles to a heat treatment and hence to crosslinking, in which apparatus an impeller is provided over a tilted bottom wall portion of the autoclave.
(2) Description of the Prior Art
As conventional heat treatment apparatus for polyolefin resin particles, there have been employed apparatus in which an impeller of a desired shape is suspended in an autoclave so as to agitate and heat resin particles together with a dispersing agent and the like in the autoclave, whereby the resin particles are subjected to a heat treatment. Apparatus equipped with conventional impellers suspended in autoclaves are show, by way of example, in FIGS. 4, 5, 6 and 7.
When a heat treatment is applied to polyolefin resin particles, it is preferable that resulting resin particles or crosslinked resin particles are obtained with spherical shapes. The formation of these resin particles into spherical shapes has been the subject of a great deal of work. When the formation of particles of the resin into spherical shapes is desired it is generally required to lower the viscosity of the resin. For this purpose, it is necessary to heat the resin to its melting point or higher. When spherical particles of crosslinked polyolefin resin are produced, it is also necessary to conduct their production at an elevated temperature (for example, the melting point of the resin or higher) so as to shorten the time required for its crosslinking reaction.
However, whenever agitation of polyolefin resin particles was attempted at such a high temperature in an aqueous medium by means of an apparatus of the above-mentioned type, it was impossible to avoid fusion-cohesion and agglomeration of the particles so that spherical particles were difficult to obtain.